Characteristics of Nanyishan Fractured Reservoir and Productivity in Chaidamu Basin, in the Western China

Li, Zhongchun ¹
(1)Research Institute of Petroleum Exploration & Development-Northwest, Lanzhou, China.

Abstract: Nanyishan E32 fractured reservoir in Chaidamu Basin of China has the common characteristics of fractured reservoirs and is also unique at genesis, lithology, identification, distribution and productivity. The reservoir is a mixture of carbonate rock, calcareous mudstone and clastic rock. The coarse particles mingle with the fine ones and there is no single and pure rock type. There are high-angle fractures, oblique fractures and horizontal fractures in this kind of fractured reservoir, which are fine and dense and connected with each other perfectly, supplying the key space for oil and gas accumulation and transportation. From the two limbs to the crest, the reservoir distributes relatively uniformly and the lithology is steady, having a feature of stable inland lacustrine deposit facies. The drainage pressure and the saturation mid-value pressure of the reservoir interval are 1.30~8.06 MPa and 3.12~10.22 MPa, respectively. In the non-reservoir interval, the drainage pressure is usually larger than 30 MPa and the saturation mid-value pressure is 80~124 MPa, which are larger than those of the reservoir interval. In the reservoir interval, circulation loss and well blowout occurred nearly in all wells during well drilling process. There were two distinct phenomena of cycle skip in SDT curves and wellhole enlargement in caliper curves, respectively. The reservoir interval also had electric logging characteristics of clasolite reservoir, such as negative anomaly of SP. Gas well productivity by natural energy was relatively low, and the low permeability was the main reason.

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.